Chapter 16 & 15

Properties and classification of matter

Kinetic Theory

Kinetic Theory—an explanation of how particles in matter behave. There are 3 assumptions of kinetic theory:1. All matter is made of small particles

2. These particles are in constant motion

3. The particles collide with each other and the walls of their container.

Solid StateThe particles of a solid are closely packed together.Most solids have a specific geometric arrangement.You can tell the chemical and physical properties of a solid based on the type of arrangement that a solid forms.

Solids have a definite shape and volume.

Liquid StateLiquids form at a melting point—the temp. that a solid begins to liquefy.

Particles in a liquid have more kinetic energy than in a solid—they are moving faster.

These particles can slide past each other allowing liquids to flow and take the shape of their container.

Liquids have a definite volume, but no definite shape.

Gas StateParticles in a gas have more kinetic energy than in a liquid.

A liquid becomes a gas through evaporation or boiling.

Gas particles have enough kinetic energy to overcome the attractions between them.

Gases have no definite shape or volume.

They can spread apart to fill the container they are in.

Diffusion—the spreading out of particles throughout a volume until they are uniformly distributed.

States of Matter

Plasma StatePlasma is the most common state of matter in the universe.

Plasma—matter consisting of positive and negative particles at very high temperatures.

When gases get very hot their particles move faster, these fast moving particles collide with greater force.

These collisions can pull off electrons, creating a charged particles

All stars (including the sun) consist of plasma.

Plasma is also found in lightning, neon light tubes, and auroras.

Expansion of MatterAs the temperature of particles increases, the particles move faster and separate.

The separation of particles causes the whole object to expand.

Thermal Expansion—an increase in the size of a substance when temperature increases. Examples:

Solid: Expansion joints in sidewalks

Liquid: Thermometer

Gas: Hot air balloon

Water: The ExceptionWater is an exception to thermal expansion because liquid water is most dense at 4°C.

Water molecules are unusual because they have highly positive areas and highly negative areas.

As the molecules move closer, the unlike charges are attracted.

This causes some empty spaces in the structure.

This empty space makes solid ice less dense than liquid water.

Solid or Liquid?Some substances have unusual behavior.

They have properties of both solids and liquids.

Amorphous solids—solids that lack the ordered structure found in crystals.

Examples: Glass and plastic

Liquid Crystals—start to flow as they melt, but do not lose their ordered arrangement completely

Examples: Liquid Crystal Displays (LCD) in watches, calculators, computers, and TVs.

Sec. 2: Properties of Fluids

Buoyancy—the ability of a fluid (liquid or gas) to exert an upward force on an object immersed in it. This is what causes ships to float.

Archimedes’ Principle—the buoyant force on an object is equal to the weight of the fluid displaced by the object.

An object will float if its density is

less than the density of the fluid it

is placed in.

Pascal’s PrinciplePressure—force exerted per unit area Pressure = Force/Area P = F/A

Pascal’s Principle—pressure applied to a fluid is transmitted throughout the fluid. Example: you squeeze 1 end of a toothpaste tube,

toothpaste comes out the other end.

Bernoulli’s PrincipleBernoulli’s principle describes how people were able to build a machine that can fly.

Bernoulli’s Principle—as the velocity of a fluid increases, the pressure exerted by the fluid decreases.

Airplane wings were designed to reduce pressure above the wings.

Sec 3: Behavior of Gases

Boyle’s Law—when volume is decreased, pressure is increased (and vice versa) as long as temperature is constant.

The equation for Boyle’s Law is P1V1 = P2V2

The subscript 1 represents initial pressure and volume, and the 2 represents final P & V.

The unit for pressure is pascals & the unit for volume is liters.

Charles’s LawCharles’s Law—the volume of a gas increases with increasing temperature (and vice versa)

The equation for Charles’s Law is V1 = V2

T1 T2

Again, 1 is initial, and 2 is final. Volume is in liters and temp. must

be in Kelvin

The Pressure-Temperature Law

As temperature increases, the pressure increases too (and vice versa)

This is why you should keep pressurized spray canisters away from heat.

Classification of Matter

Sec. 1 Composition of MatterAll materials are either made of pure

substances or mixtures.

Substance—an element or compound, definite composition

Element—a substance with atoms that are all alike Ex. Carbon (C) & Magnesium (Mg) You can find them on the periodic table!!

Compound—a substance that contains 2 or more elements combined chemically. Ex. Table salt (NaCl) & Hydrogen peroxide (H2O2)

MixturesMixture—a material made of 2 or more substances that can be separated physically.

There are 2 types of mixtures: heterogeneous and homogeneous.

Heterogeneous Mixture—different materials can be distinguished easily.

Ex. Pizza, salad, chocolate chip cookies (mmm)

Suspension—a heterogeneous mixture containing a liquid in which visible particles settle.

Ex. Mud in a pond & river deltas

MixturesHomogeneous Mixture—substances are blended evenly throughout.

Solution – homogenous mixture that remains constantly and uniformly mixed and has extremely small particles Ex. Pop, vinegar

How to Classify Matter

Element

Substance

Compound

Matter

Heterogeneous

Mixture

Homogeneous

ON PERIODIC TABLE

EX. WATER= H20

*SUSPENSION

*SOLUTION

Sec. 2: Properties of MatterPhysical Properties—any characteristic of a material that you observe without changing its substances. Ex. Color, shape, size, density, melting &

boiling point

Some physical properties describe behavior. Magnetism, conduct electricity, viscosity,

dissolving.

You can separate mixtures using physical properties. Size, color, magnetism, boiling point, etc.

Chemical Properties

Chemical Property—a characteristic of a substance that tells if it can undergo a certain chemical change. Ex. Flammability, reaction to light

Physical Changes

Physical change—a change in size, shape, or state of matter (solid, liquid, gas) The identity of the substance doesn’t change. Ex. Freezing, ripping, folding, dissolving.

Physical Changes

Physical changes DO NOT alter the identity of the original substance

A change in size, shape or state of matter is a physical change “3S”

Chemical ChangesChemical Change—a change of 1 substance to another.

Ex. Rotten eggs, rust, burning.

Detecting Chemical Changes: Odor, heat, light, sound, release gas (bubbles), color change

Separating Substances: Ex. Cleaning tarnished silver, purifying metals. A chemical change will change the substances, so it cannot

be used to separate a mixture.

Chemical ChangeThe change of one substance to another is a chemical change

6 Clues that a chemical change has occurred Color change Bubbles (not boiling) New odor Heat or Cooling Light Sound

Chemical Reaction

Chemical change happens during a chemical reaction

Never a change in the number of elements

Energy is always taken in or given off

WeatheringWeathering is how Earth’s surface changes.

Weathering is a result of both physical & chemical changes.

Physical: ice wedging (ice in cracks expands & breaks the rocks), & streams cut through softer rock.

Chemical: limestone dissolves in acidic ground water (canyons & caves are formed this way)

Caves are formed through chemical weathering.

Ice wedging or the freeze/thaw cycle breaks rocks into pieces

Conservation of MassLaw of Conservation of Mass—the mass of all substances before a chemical or physical change equals the mass of all substances after the change.

In other words: mass is neither created nor destroyed during any chemical or physical change.